In recent years, demand for portable electronic apparatuses, such as mobile phones or notebook computers, has been growing. In such electronic apparatuses, thin mobile terminals having sound functions of a videophone or video reproduction, a hands-free phone, and the like as commercial values are under development. Among such developments, there is a growing demand for high-quality sound and reductions in the size and thickness of an electro-acoustic transducer (speaker device) that is an audio component.
Currently, in an electronic apparatus, such as a mobile phone, an electro-dynamic electro-acoustic transducer is used as an electro-acoustic transducer. The electro-dynamic electro-acoustic transducer is configured to include a permanent magnet, a voice coil, and a vibrating film.
However, there is a limitation in making the electro-dynamic electro-acoustic transducer thin due to its operating principle and structure. On the other hand, Patent Documents 1 and 2 disclose using a piezoelectric element as an electro-acoustic transducer.
Moreover, in addition to the speaker device, various electronic apparatuses, such as a sound wave sensor (refer to Patent Document 3) that detects a distance to an object using sound waves oscillated from a piezoelectric element, are known as other examples of an oscillation unit using a piezoelectric element (Patent Document 4).